The present invention refers to a bearing assembly for supporting a shaft without play, and in particular to a bearing assembly for journalling a steering shaft in a steering column such as to prohibit lost motion therebetween.
U.S. Pat. No. 4,820,062 describes a bearing assembly for journalling the steering wheel shaft of a vehicle, including a number of needle-like rollers that are retained in a cage. The outer race of the rollers is circumscribed by a thin-walled bearing bush which elastically loads the rollers in radial direction. An elastic tolerance ring is press-fitted over the bearing bush and has a number of projecting ridges in equi-spaced parallel relation with one another on the peripheral surface in axial direction. As the outer diameter of the tolerance ring exceeds the inner diameter of the steering column, the elastic tolerance ring is squeezed during assembly of the bearing into the steering column, thereby being elastically deformed radially and inwardly to compress the internally fitted bearing bush in the radial and inward direction. Thus, when the bearing assembly is press-fitted into the steering column, the excess in diameter of the tolerance ring applies a preload on the slotted bush and thus on the rollers and the steering shaft so that a lost motion therebetween is prohibited.
When installing a bearing of this type in steering columns within a bore that has a maximum limit for a bearing seat, the applied preload is relatively small while a bore of minimum limit for a bearing seat effects a great preload. Thus, housings with bores of great tolerances result in significant variations of the preload. As a consequence of these tolerance variations, customers frequently experience that their demands are not met when installing the bearing in a bore of the steering column that has one or the other extreme size. Taking for example a steering column with a bore of minimum size, the preload of the bearing applied on the shaft may rise to such order that the torque and/or axial displacement force becomes prohibitive. Proposals to overcome this problem include the provision of the elastic tolerance ring with a ribbing for decreasing the preload. Conventionally, such a ribbing is formed by providing in the outer peripheral surface of the elastic tolerance ring a plurality of axial grooves that are evenly spaced about the circumference to thereby create between the grooves ridges of equal size which radially project from the outer peripheral surface. The previously addressed problem could however not be solved by the formation of such ridges because at great tolerances of the bore the bearing applies a preload on the shaft which is too low so that the radial displacement becomes prohibitive. Moreover, regardless whether the preload is too small or excessive, the attenuation behavior is adversely affected in any event.